Traditional tennis racquets have fixed strings which have no flexibility other than that resulting from their natural elasticity. As the strings are fixed, the initial tension of the strings is also fixed.
Various factors influence this tension, such as in particular the ambient temperature and hygrometry, or the duration and force of the game and, as a general rule, the tension decreases although it would be desirable to maintain it as constant as possible.
Therefore, it is desirable to render this tension adjustable to enable the players to modulate their game depending on that of their opponents. In one known design of racquet, the string tension is adjusted by means of a screw and nut device housed in the racquet handle and fastened to several longitudinal strings of the head. This arrangement presents two limits: on the one hand, only a few longitudinal strings close to the centre of the head can have their tension adjusted, and, on the other hand, the tension is still likely to vary as a function of the outside factors, with the result that a readjustment is frequently necessary.
Patent NL No. 22 409 discloses a rudimentary tensioning device employing a compressed spring. A tool must be used for driving the adjusting nut and it is observed that the range of adjustment is fairly narrow since the turns of the spring are virtually contiguous. Finally, no means for blocking the nut are provided, and it therefore is likely that the nut may become loose.